A torque converter incorporated into a vehicle automatic transmission is constructed in such a way that a front cover forming a front surface portion of a converter housing is driven in rotation by a crankshaft, torque is transmitted between blades on a pump impeller side of the converter housing and blades on a turbine runner side, and the torque is transmitted from an output shaft driven by the turbine runner to an input shaft of a transmission. In addition, the torque converter has a lock-up device for directly transmitting the torque of the engine crankshaft to the transmission in order to improve fuel consumption.
In the lock-up device, the output shaft and the front cover of the converter housing are connected by a clutch which is driven by fluid pressure (hydraulic pressure), and the torque of the engine crankshaft is transmitted directly to the input shaft of the transmission.
A torque conversion unit formed by the pump impeller and the turbine runner etc., and the lock-up device formed by a lock-up piston, an input-side rotation member, an output-side rotation member and a buffer etc. are attached by fastening (riveting) of a turbine hub and the output-side rotation member (hub clutch).
This kind of lock-up device comprises a torsional vibration reduction mechanism (also referred to below as a “damper”) interposed between the clutch and the output shaft in order to absorb and damp torsional vibration.
What is known as a damper constituting the torsional vibration absorbing mechanism is constructed here as the buffer. The damper absorbs torsional vibration produced from rotational torque when rotational torque from the input-side rotation member is transmitted to the output-side rotation member, and transmits this from the turbine hub to the output-side rotation member. The structure of the damper is an integrated structure in which a drive plate and a side plate are fixed by riveting, and the rotational force thereof is transmitted to the turbine hub via the hub clutch. The arrangement is such that torsion springs for absorbing torsional vibration are then interposed between the drive plate and the side plate, and torsional vibration is absorbed when torque is transmitted to the hub clutch.
These members are substantially disk-shaped and rotate about the crankshaft, and a number of torsion springs interposed between the drive plate and the side plate are generally disposed equally on the rotational circumference thereof. The torsion springs for limiting torsional vibration are generally constructed as an elastic vibration reducing mechanism in view of the structure thereof, and demonstrate their function by using spring resilience to damp pressure resulting from contact of the hub clutch, which is a physical external force.
A centrifugal pendulum-type vibration absorbing device has a substantially disk-shaped structure in which a pendulum member that can freely move in the radial direction in the manner of a pendulum is disposed in the vicinity of substantially the outer circumferential side and the radial side with respect to an axis of rotation. A plurality of pendulum members are disposed at fixed intervals along the circumference of a plate formed as a single piece with the centrifugal pendulum-type vibration absorbing device, and the individual weights thereof are also set in accordance with the centrifugal pendulum function.
The pendulum members are subjected to centrifugal force as a result of rapid rotation of the centrifugal pendulum-type vibration absorbing device and move to the outer circumference, so the mass balance of the centrifugal pendulum-type vibration absorbing device as a whole moves in the outer circumferential direction, and a function of damping a rapid rotational speed is demonstrated. Furthermore, changes in the mass balance of the centrifugal pendulum-type vibration absorbing device as a whole produced by any free movement having an inertia force of the centrifugal pendulum with respect to torsional vibration and rotational vibration act as a force to damp rotational movement.
As indicated above, the torsional vibration absorbing function afforded by the elastic vibration reducing mechanism of the damper, and the pendulum-type vibration damping mechanism afforded by the centrifugal pendulum-type vibration absorbing device constitute the same vibration buffering function, but the actions thereof are different. A vibration absorbing mechanism combining both the functions of the elastic vibration reducing mechanism and the pendulum-type vibration damping mechanism has therefore come to be used as a vibration absorbing mechanism within a torque converter incorporated in a vehicle automatic transmission. Various technologies have been investigated for mechanisms for imparting a centrifugal pendulum-type vibration absorbing function within a conventional torque converter damper structure.
For example, JP 5387562B2 describes a technical concept indicating the structure of a substantially circular centrifugal pendulum-type vibration absorbing device comprising centrifugal pendulum-type vibration absorbing bodies. These vibration absorbing bodies demonstrate a function of controlling vibration in the radial direction with respect to an axis of rotation, while controlling impacts between adjacent masses and the generation of abnormal noise caused thereby.
However, although that example gives a detailed description of the centrifugal pendulum-type vibration absorbing bodies, there is no mention of the specific structure installed in the torque converter or the advantage thereof, so the technical and economic benefits resulting from installation of the centrifugal pendulum-type vibration absorbing bodies are unclear.
JP 2011-504986 A describes a technical concept relating to a centrifugal pendulum-type dynamic damper for reducing torsional vibration produced in a rotary shaft. That dynamic damper has a structure in which a rotary plate, provided as a single piece with a rotary shaft, and centrifugal pendulum-type vibration absorbing bodies are housed in a plurality of housing compartments formed at fixed intervals in the circumferential direction of a rotary plate. The rotary plate comprises a hub which is attached to a crankshaft and rotates as a single piece with said crankshaft. The centrifugal pendulum-type vibration absorbing bodies are constructed in such a way as to reduce torsional vibration generated as the crankshaft rotates by moving back and forth while rolling inside the housing compartments.
However, although that example gives a description of the technical advantage of installing the centrifugal pendulum-type vibration absorbing bodies inside a torque converter, there is no mention of the specific installation structure and thus there is no description of the technical benefit, contribution to facilitating production, and economic advantage etc. resulting from a specific form of structure in which the centrifugal pendulum-type vibration absorbing bodies are installed as a single piece with a damper.